Apparatus and method for automatically controlling the molten metal bath level in a metallurgical process



P. R. MARCHANT M y .7 APPARATUS AND METHOD FOR AUTOMATICALLY CONTROLLINGTHE MOLTEN METAL BATH LEVEL IN A METALLURGICAL PROCESS Filed Nov. 1.196?

.5 TP A EM w v, M nx A TTO/PNEV United States Patent APPARATUS ANDMETHOD FOR AUTOMAT- ICALLY CONTROLLING THE MOLTEN METAL BATH LEVEL IN AMETALLURGI- CAL PROCESS Peter R. Marchant, San Francisco, Calif.,assignor to General Electric Company, a corporation of New York FiledNov. 1, 1967, Ser. No. 679,696 Int. Cl. C23c 1/00 US. Cl. 117114 2Claims ABSTRACT OF THE DISCLOSURE In the dip-forming process foraccreting metal onto a core member passed through a crucible containinga molten bath of metal, a melt of molten metal is continuously suppliedto the crucible from a holding chamber. An inverted pressure bell isdisposed in the holding chamber, and gas is introduced into the enclosedportion of the bell for exerting pressure on the surface of the moltenmetal within the bell. A liquid level sensing means is immersed in themolten metal, and gas is continuously introduced through the liquidlevel sensing means whereby a back pressure is established in thesensing means which is correlated with the level of molten metal in theholding chamber.

The dip-forming process, such as used in casting metal, is now wellknown in the art. According to this process, an elongated body such as ametal rod is typically pretreated by passing it through a straightener,and a surface cleaning apparatus, and then through a vacuum entrancechamber arranged in the wall of a crucible which contains a bath ofmolten material. The elongated core or body is passed through the moltenbath, which bath may have been the same chemical composition as that ofthe core or a different composition. The molten material in the crucibleaccretes or deposits upon the outer surface of the core therebyincreasing its cross-sectional area appreciably. After emerging from thecrucible, the resulting cast member is cooled as by. a water spray fromone or more jet nozzles at least sufiiciently so that the cast membercan be rolled or worked. From there, the cast member may be passedthrough a suitable roll mechanism where it is reduced in cross-sectionalarea and then passed to a suitable receiving means such as a take-upreel.

It is essential for the successful operation of the dipforming processthat the depth of molten metal in the crucible be controlled accurately.If the bath of molten metal is too shallow relative to the core size andspeed, full accretion will not occur and output therefore will be lost.On the other hand, if the bath is excessively deep, re-melting of thecast body will occur which results also in reduced output.

This invention has therefore as among its objects to provide a means andmethod for accurately controlling the bath depth of molten metal whicheliminates wide fluctuations in bath depth.

Other objects and advantages of the invention will best be understood byreferring to the following detailed specification, and to theaccompanying FIG. 1 illustrating in elevation a preferred embodiment ofthe invention, with the control mechanism being illustratedschematically.

In general, the apparatus of this invention employed in a dip-formingprocess, in which molten metal is accreted to a core passed through acrucible containing the molten metal, includes a holding chamberdisposed adjacent the crucible and in communication therewith. Theholding chamber, which contains a supply of molten metal, is providedwith suitable means for adjusting or regulating the level of moltenmetal, such as an inverted displace- 3,510,345 Patented May 5, 1970 mentbell, or a graphite block as disclosed in United States Pat. No.3,060,053 to Carreker et al. and assigned to the assignee of thisapplication. Gas is continuously introduced through a liquid levelsensing device immersed in the molten metal, whereby the back pressureestab lished in the device is correlated with the level of molten metalin the holding chamber. The level regulating means is adjusted inresponse to the back pressure thereby regulating the bath level withinthe holding chamber and, in turn, within the crucible.

Although the invention is described hereinbelow with reference todip-forming a copper rod, it is understood that the invention isapplicable to other metals.

Referring to the drawing, core rod 10, such as a copper rod, is suppliedto a drawing apparatus 12 located adjacent a suitable shaving apparatus14 which shaves a thin layer of metal from the periphery of the rod toremove the oxide coating and other surface contaminants therefrom. Ifdesired, other cleaning means such as chemical cleaning means may beutilized for removing the oxide coating and cleaning the surface of therod. The rod is passed through a suitable drive means, including capstan15 and drive rolls 16 contained in housing 18, and from there into tube20. Members 12, 14, 18, and 20 are sealed and interconnected by asuitable passageway, and tube 20 has connected thereto exhaust tube 22and evacuating pump 24 to maintain a vacuum in the passageway. Entryport member or nozzle 26 is mounted in the upper end of tube 20 andextends into crucible 28 which is maintained at the desired elevatedtemperature by suitable heating means such as electric induction heater30. Core rod 10 is fed through nozzle 26 and into crucible 28 where therod comes into contact with the molten copper which accretes to the rod.

Molten copper is supplied to crucible 28 from a suitable melting furnaceindicated generally by the numeral 32, which is heated by a plurality ofsilicon carbide electric radiant heaters 34. Cathode copper plates 35,or other suitable feed material of low oxygen content, is supplied tothe furnace 32 by any suitable means such as a mechanical drive means(not shown). Desirably the furnace is provided with a sloping orinclined section 36 and an integral horizontal section 38. The cathodecopper plates are charged to section 36 of the furnace through aflapper-type door (not shown), and melted gradually on the incline asthey pass to the horizontal section 38 where a pool of molten metalcollects. The molten metal flows by displacement over a weir 40 into aholding chamber 42 of the furnace described hereinbelow in greaterdetail. It is desirable that an inert or reducing atmosphere bemaintained above the melt in the furnace as well as in the dip-formingcrucible, which may be supplied through line 48 and line 49,respectively, from any suitable source (not shown). As the core rodpasses through the molten bath of metal in the crucible, copper accretesprogressively thereon thereby forming a rod of increased diameter withmolten metal substantially bonded to the core rod.

An elongated tube 52 extends upwardly from crucible 28, and theresulting cast rod having copper accreted thereto is passed out of thecrucible to the extension tube. The cast rod emerging from the crucibleand extension tube is at a relatively high temperature and is cooledsomewhat by cooling means 54, such as a water spray nozzle, before therod is passed through direction changing rolls 56. From there the castrod is directed to a suitable rolling mill and coiling apparatus (notshown) and to a storage area as desired.

Passageway or conduit 58 establishes communication between the holdingchamber 42 and the crucible 28, and molten metal will flow from theholding chamber to crucible when the level of molten metal in theholding chamber adjacent the inlet 60 of the communicating passageway 58is above the level of the passageway. An inverted pressure bell ordisplacement bell 62 is disposed within the holding chamber in order toselectively adjust the level of molten metal in the holding chamber,described hereinbelow in greater detail. The side walls of the bell areat least partially immersed below the level of molten metal contained inthe holding chamber, and desirably the bottom edge of the bell is spacedfrom the bottom surface of the holding chamber so as to enable moltenmetal to flow into the enclosed portion of the bell. The top portion ofthe pressure bell has a cylindrical extension 64 which projects upwardlythrough the upper wall of the holding chamber 42. The cylindricalextension 64 is sealed at'the top, and a first pipe 66 is mountedtherein for conducting gas from a source (not shown) through a pressurecontrol valve 68 and into the enclosed portion of the bell for applyingpressure on the surface of the molten metal contained therein. A secondpipe 7 having valve 71 is mounted in the top of the extension 64 forexhausting the gas from within the bell for relieving the pressure onthe surface of the molten metal contained therein.

During the dip-forming operation, the molten metal contained in thecrucible and holding chamber decreases. In accordance with the presentinvention, the level of molten metal is continuously measured by aliquid level sensing device. For this purpose, a sensing device 72,composed of a material substantially inert to the molten metal, isimmersed in the bath, preferably in the holding chamber as shown in thedrawings, but alternatively may be disposed in the dip-forming crucible.The sensing device is a substantially cylindrical member composed ofmolybdenum or other suitable material and provided with a longitudinalbore opening at the bottom thereof such that upon immersion in thecoating bath, communication is established between the longitudinal boreand the; interior of the crucible below the level of molten metal. Inthis manner, a gas, which is desirably inert to the molten metal, isintroduced to the molten bath from a source not shown through line 74 tosensing device 72, and bubbles to the surface of the bath. The rate offlow of gas introduced to the molten bath is automatically controlled ata constant value by pressure regulator or valve 76 and flow controlmeter 78, both of which are incorporated in line 74. Suitable gases,which may be used in either the sensing device or the displacement bell,in clude the inert or reducing gases, for example, nitrogen, argon,carbon dioxide, natural gas, etc.

When gas is introduced to the molten bath, the back pressure, or levelindicating pressure, in the sensing device is measured. This pressure isa measure of the fluid level above the outlet of sensing device. Thisback pressure actuates differential pressure transducer 80. The poweroutput from the transducer is supplied to control valve 68 via line 82which automatically regulates the gas pressure inside the inverteddisplacement bell above the molten metal. It will be observed that thepressure within the enclosed portion of the bell regulates the level ofmolten metal in the holding chamber and, in turn, the level in thecrucible. This control substantially eliminates wide fluctuations inbath depth thereby rendering the process more efiicient and providing amore uniform product.

The present invention is particularly useful in the dip forming processfor casting copper on a copper core rod. It should be understoodhowever, that the process is also applicable for use in castingdissimilar metals, such as copper or steel.

I claim:

1. In an apparatus for the continuous casting of metal which includesthe steps of continuously passing an elongated core member through abath of molten metal contained in a crucible thereby accreting metal tosaid core member, the improvement comprising:

(a) a furnace for melting feedstock having an integrally arrangedholding chamber disposed adjacent said crucible for containing a supplyof molten metal; I

(b) communication means opening to said holding chamber and saidcrucible for establishing communication therebetween;

(c) an inverted pressure bell disposed in said holding chamber spacedfrom the bottom surface thereof and having its side walls at leastpartially immersed below the level of molten metal contained in saidholding chamber, and including means for introducing gas into theenclosed portion of said bell for applying pressure on the surface ofmolten metal contained therein;

(d) a liquid level sensing means immersed in the molten metal;

(e) means for continuously introducing gas substantially inert to themolten metal through said liquid level sensing means whereby a backpressure is established in said sensing means which is correlated withthe level of molten metal contained in said holding chamber; and

(f) means responsive to said back pressure for actuating the pressurewithin the enclosed portion of said bell thereby controlling the levelof molten metal in said holding chamber.

2. In a method for the continuous casting of metal Which includes thesteps of continuously passing an elongated core member through a bath ofmolten metal contained in a cruible thereby accreting metal to said coremember, the improvement comprising:

(a) continuously supplying molten metal to said crucible from a holdingchamber arranged adjacent said crucible and in communication therewith;

(b) continuously introducing a gas into the enclosed portion of aninverted pressure bell disposed in said holding chamber and having itsside walls at least partially immersed below the level of molten metalcontained in said holding chamber thereby applying pressure on thesurface of molten metal contained therein;

(c) continuously introducing gas substantially inert to the molten metalthrough a liquid level sensing means immersed in the molten metalwhereby a back pressure is established in said sensing means which iscorrelated with the level of molten metal contained in said holdingchamber; and

(d) continuously adjusting the pressure within the enclosed portion ofsaid bell in response to said back pressure thereby controlling thelevel of molten metal in said holding chamber.

References Cited UNITED STATES PATENTS 310,994 1/1885 Farmer 164-275867,659 10/1907 Hoopes et a1 164-275 X 2,593,197 5/1952 Rough 65-346 X2,664,852 1/ 1954 Chadsey 118-49 2,988,099 6/1961 Langhans 137-403 X3,060,053 10/ 1962 Carreker et a1 164-86 X 3,104,678 9/1963 Cole 137-4033,200,971 8/1965 Trethewey 137-403 X 3,384,150 5/1968 Newsome 164-337 XMORRIS KAPLAN, Primary Examiner US. Cl. X.R.

